Duc Long Bus Station is located 3km east of the city center and has buses to other provinces and Laos. A xe om should be no more than 20,000d, but you may be able to bargain it down to 15000d. There are local buses to the city center, but they are not frequent.
There are frequent buses to Quy Nhon (3 hours, 80,000d as of March 2011). Mai Linh buses depart at 0730 and 1330. Mai Linh has a night bus that leaves Da Nang at 20:45 and reaches Pleiku in the early morning (230,000 as of Oct 2012). There are also frequent buses to and from Buon Ma Thuot.
Mai Linh and Dien Hong have buses to Laos - Attapeu, Xekong, and Pakse. Mai Linh buses to Attapeu (175,000 as of March 2011) take around 7 hours, to Pakse around 12 hours. Departure in Attapeu is at 0700 and in Pleiku 0730. The fares include lunch in Ngoc Hoi.
A xe om from the city center is likely to take 30,000d, a taxi should be between 50 and 100,000d. You're unlikely to find any xe oms on arrival in Pleiku airport. If you want to save money, you could walk or take a taxi to the main road and take a bus from there (buses from the north - Kontum, Da Nang etc - pass by there). Turn left as you leave the airport building and walk along the barracks.
Biển Hồ - A lake a few kilometers north of Pleiku.
Minh Thanh Pagoda - A nice pagoda adjacent to a temple that can be visited for free in the center of the city (as of December 2011). Look out for the picturesque illustrations of how people will supposedly be punished in hell.
In Banlung it is possible to buy a ticket all the way to Pleiku for USD 12. Bus changes after the border. Vietnamese visas must be prearranged (preferably, from Phnom Penh) and are not available at the border.